1. Field of the Invention
The present invention relates to a battery pack.
2. Description of the Related Art
Portable terminal devices such as cellular phones, PDAs (Personal Digital Assistants), notebook type computers, etc. use chargeable batteries such as lithium ion batteries as power source. A chargeable battery is charted by being connected to commercial power source.
However, one can not always use commercial power source when he/she is outdoors. In this case, the chargeable battery might run down while one uses his/her portable terminal device. Therefore, one can not use his/her portable terminal device for a long time outdoors.
Unexamined Japanese Patent Application KOKAI Publication No. 2001-178017 discloses a battery pack comprising a solar panel which converts optical energy into electrical energy. In a case where commercial power source can not be used, a chargeable battery in the battery pack is charged by the solar panel.
However, the charging speed by the solar panel varies in accordance with the weather. Further, the remaining amount of electrical energy that can be supplied by the chargeable battery can not be known from the appearance.
To know the remaining amount of the chargeable battery, a device for measuring the remaking amount of the chargeable battery must be used. In other words, a user of a portable terminal device can not know the remaining amount of a chargeable battery unless he/she carries a measuring device.
Generally, users do not carry a measuring device. Therefore, those users might use their portable terminal devices although there is little energy left in the chargeable battery, and have the chargeable battery run down while they are using the device.
The content of U.S. Pat. No. 6,384,570, which corresponds to Unexamined Japanese Patent Application KOKAI Publication No. 2001-178017, is incorporated herein by reference.
Accordingly, an object of the present invention is to provide a battery pack which shows the remaining amount of electrical energy that can be supplied.
To achieve the above object, a battery pack according to the present invention comprises:
a battery which stores electrical energy;
a remaining amount deriving unit which derives a remaining amount of the electrical energy stored in the battery; and
a first showing unit which shows the remaining amount derived by the remaining amount deriving unit.
The remaining amount deriving unit may include: a resistor circuit which is connected to the battery; and an adding-up unit which derives the remaining amount of the electrical energy stored in the battery by adding up a value of a current flowing through the resistor circuit.
The first showing unit may include a plurality of light emitting elements, and light up corresponding number of the light emitting elements corresponding to the remaining amount derived by the adding-up unit.
The battery pack may be connectable to an external power source, and the battery may be a chargeable battery, and may be charged with electrical energy supplied from the external power source.
The battery pack may further comprise a solar panel which converts optical energy into electrical energy, and the battery may be a chargeable battery, and may be charged with electrical energy obtained by conversion by the solar panel.
The battery pack may be connectable to an external power source, and in a case where the battery pack is connected to the external power source, the battery may be charged with electrical energy supplied from one of the solar panel and the external power source.
The battery pack may further comprise: a level deriving unit which derives a level of electrical energy supplied from the solar panel; and a second showing unit which shows the level derived by the level deriving unit.
The second showing unit may include a plurality of light emitting elements, and light up corresponding number of the light emitting elements corresponding to the level derived by the level deriving unit.
The battery pack may be connectable to an external device, and when connected to the external device, may supply electrical energy from one of the battery, the solar panel, and the external power source to the external device, and
in a case where electrical energy is supplied from one of the solar panel and the external power source to the external device, the battery may be charged with electrical energy from the one of the solar panel and the external power source.
The battery pack may further comprise: a specifying unit which specifies which of the battery, the solar panel, and the external power source is a supply source of electrical energy which is supplied to the external device; and a third showing unit which shows the supply source specified by the specifying unit.
The specifying unit may determine whether the battery is charged or not, and in a case where determining that the battery is not charged, may specify the battery as the supply source.
The battery pack may further comprise: a first level deriving unit which derives a level of electrical energy supplied from the solar panel; and a second level deriving unit which derives a level of electrical energy supplied from the external power source, and
the specifying unit may determine which of the level derived by the first level deriving unit and the level derived by the second level deriving unit is higher than the other in a case where it determines that the battery is charged, may specify the solar panel as the supply source in a case where it determines that the level derived by the first level deriving unit is higher, and may specify the external power source as the supply source in a case where it determines that the level derived by the second level deriving unit is higher.
The third showing unit may include a first light emitting element which indicates that the supply source is the battery, a second light emitting element which indicates that the supply source is the solar panel, and a third light emitting element which indicates that the supply source is the external power source, and
the specifying unit may light up the first light emitting element in a case where it specifies the battery as the supply source, may light up the second light emitting element in a case where it specifies the solar panel as the supply source, and may light up the third light emitting element in a case where it specifies the external power source as the supply source.